Synthesis, crystal structure, characterization, and catalytic properties of TNU-9

Suk Bong Hong, Hyung-Ki Min, Chae-Ho Shin, Paul A. Cox, Stewart J. Warrender, Paul A. Wright

Research output: Contribution to journalArticlepeer-review

80 Citations (Scopus)

Abstract

The synthesis, crystal structure, characterization, and catalytic properties of the novel mediumpore zeolite TNU-9 (framework type TUN), one of the most crystallographically complex zeolites known to date, are described. TNU-9 was found to crystallize under hydrothermal conditions at the expense of a lamellar precursor over a very narrow range of SiO2/Al2O3 and NaOH/SiO2 ratios and in the presence of 1,4-bis(N-methylpyrrolidinium)butane and Na+ ions as structure-directing agents. A combination of molecular modeling and Rietveld refinement using synchrotron powder diffraction data confirms the proposed topology of as-made TNU-9 and suggests three or possibly four different sites for the organic within the complex pore structure. The proton form (H-TNU-9) of this new medium-pore zeolite exhibits exceptionally high hydrothermal stability, as well as very strong acidity. When compared to H-ZSM-5, H-MCM-22, H-mordenite, and H-Beta, H-TNU-9 displays unique shape selectivities for the acid-catalyzed reactions of monoaromatic hydrocarbons such as the disproportionation of toluene and the isomerization and disproportionation of m-xylene. In particular, for the isomerization of m-xylene, the ratio of isomerization to disproportionation increases steadily to values in excess of 50 with prolonged time on stream and a high p/o xylene ratio is observed in the products, achieving a value of ca. 6 after only a short time on stream. These results are rationalized on the basis of the unique pore topology of TNU-9.

Original languageEnglish
Pages (from-to)10870-10885
Number of pages16
JournalJournal of the American Chemical Society
Volume129
Publication statusPublished - 5 Sept 2007

Keywords

  • STRUCTURE-DIRECTING AGENTS
  • ZEOLITE MCM-22
  • SKELETAL ISOMERIZATION
  • POWDER DIFFRACTION
  • P-XYLENE
  • DISPROPORTIONATION
  • IONS
  • NMR
  • TOPOLOGY
  • TOLUENE

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